This doesn't involve traditional mathematics concepts, but I'm relying heavily on visual explanations in my mathematical explorations of discrete geometry, which you can find at https://quivergeometry.net.

Probably the cleanest examples of where visualization makes things very clear is explaining the groupoid structure of paths [1], and how to generate lattice quivers [2].

But I also enjoy some of the aesthetic qualities of the sections on coverings [3] (intricate), vertex colorings [4] (very colorful!), toroidal lattices [5], and products of quivers [6]. The last in particular involves trying to understand products from both an algebraic and geometric perspective, and 3D visualization is especially helpful there, giving intuition for how a certain product slices off hexagonal pieces of a hypercube.

[1] https://quivergeometry.net/qg/paths/

[2] https://quivergeometry.net/qg/lattice-quivers/

[3] https://quivergeometry.net/qg/covers/

[4] https://quivergeometry.net/qg/colorings/

[5] https://quivergeometry.net/qg/toroidal-lattices/

[6] https://quivergeometry.net/qg/quiver-products/